Japanese published sources often give Type 1 Model 1 range as 1620km (~1000 statute miles) without drop tanks. In terms of practical range, for planning purposes in covering the Malaya invasion the IJA considered the Type 1's radius to be 500km (310 miles) with 30 minute CAP (according to Senshi Sosho vol 34 p. 241) presumably w/o tanks, which were apparently in short supply, though could be fitted to Model 1's in contrast to what some sources say.
On the opening day of the war 64th Sentai Type 1's raided Butterworth AF near west coast of Malaya from Duong Dong island off Indochina coast, which is around 415 miles one way. By even the next day the Type 1's had benefit of the newly seized base at Singora, Thailand near the Malaya border as refueling stop (and shorter ranged Type 97's were immediately based there), but AFAIK the first mission was unrefueled, but only brief strafing attack. Some examples of Type 1 escort missions in early Pacific War:
-Bangkok to Rangoon ~350 miles
-Ipoh to Singapore ~300
- Kahang, Malaya to Palembang, Sumatra ~370, the 59th Sentai was based there, 64th still at Ipoh which is 585 miles from Palembang, there are pictures of 64th's Type 1's at Ipoh with drop tanks at around that time, but OTOH then they might have stopped going or returning at the closer bases
-Palembang (once it was seized) to Kalidjati AF on Java ~400
-Shortland Isl. to Henderson Field on Guadalcanal (in early '43) ~330
Joe